Lecture 16: Composition of fruits and veg Flashcards
max moisture content at complete turgor yield ____ turgidity
max
how can a plant have complete turgor?
having unlimited supply from mother plant
describe the conditions (TSS, OP and TP) at a very tender stage of a crop
low total soluble solids (TSS)
low OP
low TP
describe the conditions for optimal maturity stage of produce
high OP and TP = high turgidity
- balanced starch, celulose and pectin
describe the conditions of overmaturity/ripening
fruits:
- breakdown of starch and pectin
- loss in cell wall strength
- decr in turgidity
veg
- sugar becomes starch
- loss of TSS
- low OP
- low turgidity despite high cell wall strength
what is imp about dietary fiber consumption?
- provides non-digestable bulk to the diet
- helps to control appetite = incr retention time for nutrients
- restricts calorie food intake
- delays absorption of glucose and fat after a meal
what are 2 main categories of dietary fibers? example of each?
insoluble: cellulose, hemicellulose, lignin
soluble: pectin and gums
describe resistant starches
- new class of fiber
- not easily digestible
- retains longer in the system
- good for diabetic patients
describe straight chain starches
amylose w/ alpha 1,4 bonds
describe branched chain starches
amylopectin (alpha 1-4 and 1-6 bonds)
what bonds does cellulose have
beta 1-4 linkages
what major enzymes breaks down starches?
amylase and beta-galactosidase
industrially, starch is obtained from what?
potato and corn
describe pectic substances
- imp for texture of produce due to structure forming ability
- polymer of methyl ester of galacturonic acid
- forms gel or viscous colloidal suspensions (eg. jam = pectin + sugar + acid + cooking)
what are rich sources of pectin?
apple and citrus fruits
what are 4 types of resistant starches?
RS1:
- physically inaccessible or digestible
- found in seeds and unprocessed whole grains
RS2
- occurs in natural granular form (uncooked potato, high amylose corn, green banana)
RS3
- formed when starch containing foods are cooked and cooled (eg. bread or retrograded high amylose corn)
RS4
- starches that have been chemically modified to resist digestion
- not found in nature
what are main components of jam?
pectin
sugar
acid
what is LMP? describe it.
low methoxyl pectin
- forms gel with Ca without sugars
- used in making diabetic jellies
how does pectic substances affect fruit juices?
- increases viscosity
- incr cloudiness
- colloidal suspension
what is PME? describe it.
pectin methyl esterase
- a natural enzyme that can hydrolyze pectin
how can you decrease cloudiness of apple juice?
increase PME to hydrolyze pectin
then inactivate it during pasteurization
what is calcium chloride treatment used for? how does this occur?
firming fruit slices
Ca forms a gel with pectin (LMP) to increase gel strength or structural rigidity
how does pectin affect filtration in juice making?
how can this be prevented?
- it delays filtration
- can facilitate filtration by using PME to breakdown pectin and using amylase to breakdown starch
____ are the major components of the cytoplasm
protein
define dry weight basis
%DB = (wt x 100) / dry mass
define wet wt basis
%DB = (wt x 100) / wet mass
during storage, how do proteins affect OP of AA? how does this affect nutrition of the crops?
lowers OP of AA
increases nutrition of crops
what are common plant proteins?
albumins
globulins
gliadins
glutenin
what does gluten consist of?
gliadins and glutenins
what is gluten imp for?
dough rheology
what are fats and oils prominent in?
protective tissues (cuticle, epidermis, corky layers)
what does the nutritional value of a fat/oil depend on?
degree of unsaturation
what are examples of oils rich in sat FAs?
coconut and palm kernel oils
what are examples of oils rich in unsat FAs?
corn
peanut
olive
soybean
how many double bonds are in oleic acid?
in linoleic?
in linolenic?
in stearic?
oleic: 1 DB
linoleic: 2 DB
linolenic: 3 DB
stearic: no DB (saturated)
how are organic acids formed in F&V?
by products of metabolic activities
where are organic acids normally stored?
in the vacuole
what are dominant organic acids?
citric and malic
others: tartaric, oxalic, isocitric
what is used as a common food acidulant? why?
lime and lemons
they have more than 3% organic acid
what is EPA? describe it
- eicosa pentenoic acid
- omega 3 FA
- found in large amounts in brain nerve
- v imp in immune system function
- found in oily fish, seeds and nuts
how is vit A present in F&V?
how is it converted to vit A?
as pro-vitamin A (beta-carotene) which is converted to vit A in digestive system
why is Ca in spinach not bioavailable?
it is bound to oxalic acid
what are 3 major classes of pigments in F&V?
chlorophylls
carotenoids
falvonoids
describe chlorophylls
- normal green pigments
- imp for photosynthetic activity
- found in chloroplast (chlorophyll a and b)
- broken down by enzyme chlorophyllase
what color are carotenoids?
yellow, orange
they are masked by chlorophylls in green leaves
describe solubility of carotenoids
fat soluble
where is beta-carotene found?
lycopene?
xanthophylls?
beta-carotene: carrot
lycopene: tomato
xanthophylls: radish
where are carotenoids most present in plants?
chromoplasts
how does chlorophyll (green) become phyophitin (olive green)
loses Mg
gains H+
how does phyophitin (olive green) become phyophobide (brown)
loses phytol
how does chlorophyllin (bright green) become phyophobide (brown)
loses Mg
how does chlorophyll (green) become chlorophyllin (bright green)
loses phytol
how does chlorophyllin (bright green) become chlorins (purpurins colorless)
H+ or O2
how does phyophitin (olive green become chlorins (colorless)
O2
which pigment is responsible for bright colors in F&V?
flavonoids
what are classes of flavonoids?
anthocyanins:
- red, blue, purple
- found in sap of fruits, stems leaves roots
anthoxanthins:
- yellow
- shade is pH dependent
catechins
leucoanthocyanins:: colorless but forms brown pigments
what does the shade of anthocyanin depend on?
what colors are they in low, medium and alkaline pH?
pH
low pH: red
with increasing pH: violet
alkaline pH: blue
where are anthocyanins found?
sap of fruits, stems, leaves, roots
what happens when tannins reacts with skin?
- produce tan color
- produced by polymers of catechin in reaction with proteins of skin
what happens when tannins reacts w/ metal ions?
what is this commonly used for?
dark colors
used in making inks
what is the dark color of coffee and tea from?
tannins
what are anti-nutritional factors? examples?
- foods that can cause allergies, loss in memory, convulsions, paralysis, etc…
- eg. excessive consumption of cabbage can cause hyperthyroidism (decreases iodine absorption)
how can you cope with anti-nutrients?
inactivate toxins by cooking
what happens when soybeans are soaked before cooking?
it removes thermo-labile toxic peptides (protease inhibitors)
